1. Field of the Invention
This invention relates to apparatus and processes for generating hot water and/or steam for use in the petroleum, chemical, medical, food, heating, and other manufacturing and non-manufacturing industries. The invention has application in these industries for generation of process steam for hydrocarbon heating and petroleum refining, manufacture of chemicals and commercial food products, cleaning, laundries, and space heating.
2. Description of Related Art
For the generation of steam and hot water, almost half of all U.S. industrial watertube boilers are fired on natural gas. Within a specific industry, the chemical, petroleum refining, and food industries are the largest boiler users with over half of the energy consumed through the use of natural gas. In addition, due to current fuel pricing and emissions concerns, the demand for natural gas boilers is increasing. Heretofore these boilers have been a major source of NOX emissions. Within some areas having imposed NOX emission regulations, expensive postcombustion equipment must be installed which can double the cost of a new packaged watertube boiler.
At present most installed watertube boilers are fired by conventional burners of the diffusion flame type. The conventional diffusion flame burners in these boilers operate with relatively poor thermal uniformity and high noise output and develop undesirably large amounts of harmful emissions, particularly NOX and CO. To effectively reduce these emissions below 25 parts per million (ppm) requires complex downstream cleanup methods, such as Selective Catalytic Reduction. The need has thus been recognized to improve the thermal and emissions performance of these boilers by installing more efficient and cleaner operating radiant burners while maintaining cost competitiveness. For firetube boilers, radiant burners have been successfully employed based on the systems and methods of U.S. Pat. No. 4,519,770. No structural modification of the boiler was required to maintain the boiler's performance. No comparable method had been developed to introduce radiant burners into watertube boilers without major reductions in performance.